Synchronized chair seat and backrest tilt control mechanism

• US 6,010,189 A
• Filed: 04/01/1999
• Issued: 01/04/2000
• Est. Priority Date: 03/12/1997
• Status: Expired due to Term

• Current Assignee: L&P Property Management Company (Leggett & Platt Incorporated)
• Original Assignee: Leggett & Platt Incorporated
• Inventors: Young, David A., Hybarger, Kenneth C., Johnson, LeRoy B., Zeeuw, Bryan H., Crossman, Philip E.
• Primary Examiner(s): Cuomo, Peter M.
• Assistant Examiner(s): Allred, David E.
• Application Number:
  US09/285,151
• Time in Patent Office: 278 Days
• Field of Search: 297/300.8, 297/300.7, 297/300.6, 297/300.2, 297/300.1, 297/302.7, 297/301.7, 297/302.4
• US Class Current: 297/300.8
• CPC Class Codes: A47C 1/03238 by means of peg-and-notch or pawl-and-ratchet mechanism
• CPC Class Codes: A47C 1/03255 with a central column, e.g. rocking office chairs
• CPC Class Codes: A47C 1/03266 with adjustable elasticity
• CPC Class Codes: A47C 3/30 with vertically-acting fluid cylinder

Abstract

A chair control mechanism is provided for use on a chair having a separate seat 14 and backrest 16 that move with respect to a base 12 of the chair. The mechanism 22 includes a housing 26 supported on the base, and brackets 28, 30 secured to the seat and backrest. The seat bracket 28 is supported on the housing for pivotal movement about a horizontally extending front pivot axis 68 between an upright position and a reclining position, and the front pivot axis is located adjacent the front end of the housing. The backrest bracket 30 is supported on the housing for pivotal movement about a horizontally extending rear pivot axis 80 that is located rearward of the front pivot axis. A mechanical linkage 70, 78 is connected between the brackets at a position spaced rearward of the rear pivot axis relative to the housing for transmitting pivoting movement between the brackets, and a spring assembly 32 is connected between the housing and the backrest bracket for biasing the seat and backrest toward the upright position. A forward travel-stop control assembly 38 is provided on the mechanism for adjusting the forward most position of the seat and backrest, as is a tilt control assembly 36 which permits the seat and backrest to be locked against tilting movement. The tilt control assembly 36 includes a locking plate 102 supported on the housing for relative translational movement between an extended position in which the locking plate is received in an aperture of the backrest bracket to lock the backrest bracket from further pivotal movement, and a retracted position removed from the aperture to allow further pivotal movement of the seat and backrest. A locking pawl 106 is supported on a lever 104 of the tilt assembly and engages the lock plate 102 to retract and extend the plate when the lever is rotated. In addition, a clutch is interposed between the actuating lever and the locking pawl for exerting a rotating force on the locking pawl to move the locking pawl from the second position when the actuating lever is rotated. The rotating force of the clutch is smaller than the friction force that is exerted on the locking plate when the pivoting force of the spring assembly 32 is exerted on the locking plate such that the locking plate can only be retracted when the friction force is reduced to a magnitude less than the rotating force.

Claims

1. A chair control mechanism for use on a chair having a base on which a seat and backrest are supported, the seat presenting a front which is opposite the backrest, the mechanism comprising:

a housing supported on the base;

a seat bracket supported on the housing for pivotal movement about a horizontally extending front pivot axis between an upright position and a reclining position;

a backrest bracket supported on the housing for pivotal movement about a horizontally extending rear pivot axis between an upright position and a reclining position, the backrest bracket being linked to the seat bracket and presenting a front end forward of said rear pivot axis that moves toward the housing when the brackets are pivoted toward the upright position and away from the housing when the brackets are pivoted toward the reclining position, said front end having a downwardly extending shoulder;

a spring assembly connected to the housing and the backrest bracket and biasing the brackets toward the upright position;

a travel stop positioned on a lower surface of said housing between the housing and the front end of the backrest bracket, the stop including a plurality of steps of varying heights;

a lever connected to said housing and having a rotational axis; and

a pawl operatively connected to and extending radially from the lever and engaging the travel stop, the lever being movable to shift the stop in fore and aft directions between a plurality of positions in which different ones of the steps are interposed between the lower surface of said housing and the shoulder of the front end of the backrest bracket to limit the travel of the brackets toward the upright position.

2. A mechanism as recited in claim 1, wherein the lever is rotatable to shift the stop between the plurality of positions, the lever being supported on the housing.

3. A mechanism as recited in claim 1, wherein the backrest bracket includes a pair of laterally spaced side walls each presenting a depending said shoulder at the front end of the backrest bracket, and the travel stop includes a pair of laterally spaced legs aligned with the shoulders and interposed between the shoulders and the housing, and a cross piece connecting the legs together, the legs presenting the plurality of steps of varying heights, and the cross piece presenting an aperture within which the pawl of the lever is received.